The present invention relates to a process and apparatus for material preparation and to a method for analysis therewith, by processing a material by forming a cut face and/or a rift therein, in particular, for preparing a sample which serves advantageously for analysis, observation, record or the like (in the following, denoted sometimes as analysis etc.). More particularly, the present invention relates to a process and apparatus for material preparation adapted especially to deal with materials which are subject to deformation, destruction and denaturing, including biological objects, organic and inorganic substances, chemical products and so on, as well as to a method for analysis therewith.
For subjecting a material, especially among those, for example, biological bodies, such as plant seeds, and others, as a sample to a spectroanalysis, it is necessary to prepare a mirror-finished cut face of the material. On the other hand, for examining a sample by mass spectrometry by penetrating through the sample with a laser beam, the sample should be cut to form a slice of a specific thickness. For the device for preparing such a mirror-finished face of a sample by forming therein a cut face and/or a rift, a sliding cutter or a rotary cutter is used.
A sliding cutter operates by sliding a sharp blade and is adapted for slicing, for example, an animal tissue, such as liver, embedded in a soft substance, such as paraffin. However, the sliced tissue is apt to be deformed or destroyed by the pressure of the cutter blade. In particular, in the case of slicing a tissue, such as a stalk or a leaf, of a plant, which contains silica components, such as plant opal, the steel knife may be nicked by such silica and scars, such as knife marks, may be left on the resulting sliced sample.
A rotary cutter operates with a rotary cutting element, such as a diamond saw, which may encounter a similar disadvantage of deformation and destruction of the tissue by the cutter pressure as in the sliding cutter mentioned above, with a further defect that the cut sample is apt to suffer from denaturing due to the frictional heat upon cutting. For evading such a defect, cutting oil is used for the purpose of cooling and prevention of oxidation. In the case of a biological sample, cutting oil is absorbed in the cut sample easily and is detected upon the spectroanalysis as a contaminant component, reducing the analysis accuracy.
In both cutter arrangements, the material to be cut is fixedly held by embedding it in, for example, a paraffin wax or a resin, in order to immobilize the material upon cutting, which may cause also a decrease in the accuracy of the analysis by a possible interminglement of such holding material into the cut sample upon cutting.
A first object of the present invention is to provide a process for material preparation in which a material can be processed by forming a cut face and/or a rift therein while preventing deformation, destruction and denaturing of the material in a simple way using an apparatus of simple construction.
A second object of the present invention is to provide a process for material preparation in which a material can be processed by forming a cut face and/or a rift therein and preparing an examination surface at a predetermined position and at a definite angle of inclination while preventing deformation, destruction and denaturing thereof in a simple way, so as to obtain a sample to be examined by analysis, observation, recording or the like at a high accuracy, using an apparatus of simple construction.
A third object of the present invention is to provide a material preparing apparatus adapted for realizing such a material preparation as above.
The present invention resides in the following process and apparatus for performing the material preparation:
(1) A process for effecting preparation of a material, comprising
fixing the material on a holding unit,
freezing the material with dry ice, while replacing the gas-phase with the evolved carbon dioxide gas and
cutting the material by a cutter so as to form a cut face and/or a cut rift.
(2) The process as defined in the above (1), wherein the material is embedded in a filler filled in the holding unit and the filler is frozen in this state by dry ice to solidify, before the material is cut by the cutter.
(3) The process as defined in the above (1) or (2), wherein the cut surface, resulting after the cut face and/or the cut rift is formed by the cutter, is polished by the cutter to attain a mirror surface finishing.
(4) The process as defined in any one of the above (1) to (3), wherein the material is a sample for analysis, observation or recording.
(5) A material prepared by the process as defined in any one of the above (1) to (4).
(6) An apparatus for effecting material preparation comprising
a holding unit having one or more holders,
a settling means for settling the material held in the holder,
dry ice wells disposed so as to effect freezing of the material held in the holding unit and to effect a gas phase replacement and
a cutting space for permitting the cutting of the material by a cutter in a state frozen by dry ice with a gas phase replacement to form a cut face and/or a cut rift.
(7) The apparatus as defined in the above (6), wherein a plurality of the holders are arranged in a row.
(8) The apparatus as defined in the above (6) or (7), wherein it further comprises a mount which has a support for supporting the protruding portion of the material protruding from the holding unit and which is disposed on the holding unit disengageably.
(9) The apparatus as defined in the above (8), wherein the mount has an affixing means for affixing the cut off protruding portion.
(10) A method for effecting analysis, in which the material as defined in the above (5) is used as the sample.
The material to be subjected to the material preparation according to the present invention is processed by forming a cut face and/or a cut rift therein. For such a material, every one subject to deformation, destruction and denaturing may be mentioned, wherefor especially materials for samples for analyses etc. are particularly adapted.
Such a material may be those of biological, organic and chemical origins. Specific examples thereof include seeds, stalks, leaves and roots of plants and tissues of plants and animals including human beings. They may be those for use in applications other than a sample. Materials other than the above include, for example, materials for slicing a wafer from a silicon crystal, easily deformable textiles and others.
Such analysis, observation and others using a sample obtained by the material preparation may comprise every practice of analysis, observation, recording and so on to be carried out on the cut face or on the cut rift of the sample, including those in which mathematical processing is employed, such as for example, spectroanalyses using electromagnetic wave (including IR spectroscopy, Raman spectroscopy, X-ray fluorometry and chromatic differential spectrophotometry) and mass spectrometry, and further, those in which observation, determination and recording of an image is included, such as for example, microscopy (including electromicroscopy), TV-image analysis, photography, visual inspection and so on.
According to the present invention, such a material subject to deformation, destruction or denaturing is held on a holding unit and the material is frozen substantially instantaneously by dry ice while replacing the ambient atmosphere by carbon dioxide gas, whereupon the material is cut to form a cut face and/or a cut rift to effect the material preparation. Dry ice is a solid product of carbon dioxide produced by cooling and compressing carbon dioxide gas, for which a product having a grain size of 0.1-5 mm, preferably 0.1-2 mm, may be employed. It is enough to place dry ice at a portion capable of cooling and freezing the material and replacing the ambient atmosphere with carbon dioxide gas, while it is preferable to place dry ice around and above the material so as to cover it.
The material should be held fixedly on the holding unit during the cutting thereof. The fixation of the material may be realized using a settling member arranged in the holding unit or by filling a filler in the holding unit and making use of the adhesion force of the filler itself or, further, by solidifying the material by cooling with dry ice. As the filler, a substance capable of solidifying at a lower temperature, such as a putty (for example, based on silicone or on aqueous acrylic resin) or water, may favorably be employed due to its better processability, while it is permissible to use a polymerized or condensed substance, such as a resin.
The holding unit may be constructed in such a manner that the material is held partly so as to protrude a part of the material out thereof and to fix the material by a settling means. It is enough that a holder formed in the holding unit is constructed so as to enable the holding of the material, but the holder may preferably have a form to match the contour of the material so as to permit the holding of the material after the cutting. However, the holder may not necessarily be constructed to correspond completely to the contour of the material and may preferably have a form somewhat larger but roughly adapted to the contour of the material and, by filling the holder with a filler, such as putty or water, to embed the material therein. The holder may preferably be provided in plural numbers, wherein it is efficient and favorable to arrange them in one or more rows within one and the same plane so as to enable cutting of the materials by one single action of the cutter simultaneously. When a plurality of rows of the holders are used, they may be arranged in a form of a lattice or honeycomb.
The settling means is a member serving to settle the material held in the holder and it may preferably comprise a resilient member arranged so as to permit the settling of the material held in the holder by pressing onto the material under such a pressure that no damage of the material is caused in accordance with the configuration held in the holder but the material is settled in a fixed state. The holder and the settling member may be provided in an integral form. If the holding unit is provided with a plurality of holders, the settling members are also disposed correspondingly. For example, when the holders are arranged in a row, the settling members may be constructed in a corresponding form, namely, they may be in a form of an elongated arm or in a comb-like form.
It is possible to use, as the settling member, a filler, so long as the construction of the holder permits. Thus, if the holder is constructed in a form of a cavity, the gap between the material inserted in the cavity and the cavity wall may be filled with a filler, such as a putty, whereupon the filler is caused to solidify to attain a firm fixation of the sample. For the filler, a sheet-formed one, such as both-sided sticky tape, may also be used.
Dry ice wells for accommodating dry ice for effecting freezing of the material held on the holding unit and gas phase replacement may be arranged in the holding unit integrally therewith or separately on a mount or in a portion between the mount and the holding unit. Dry ice may favorably be piled in the dry ice wells arranged in a form of a groove surrounding the holding unit and serve an anchoring function for preventing floating of dry ice particle due to the wind pressure caused by the action of cutter rotating at a high speed, while they may simply be piled around and above the holding unit.
A cutting space is arranged to permit cutting, by a cutter, the material held on the holding unit to form a cut face and/or a cut rift. The cutter is arranged in the holding unit integrally therewith or independently therefrom. In general, cutters in cutting arrangements, such as a high performance slicer for semiconductor wafers and so on, may be used as such, while a cutter using a cutting lever having the fulcrum at one end of the holding unit may also be used in a simple cutting. Here, the holding unit is assembled on the cutting arrangement under positioning so as to permit the cutting of the sample at a portion protruding from the holder. When a plurality of samples are put on a plurality of holders, they are disposed in such an arrangement that all the samples are cut at once and in the same plane. In the case of, for example, a plurality of holders arranged in a row, cutting of the materials is performed by causing the cutter of the holding unit to move in the direction of the row. For the cutter, any voluntary type including a sliding cutter and a rotary cutter may be used, while preference is given to a rotary cutter having cutting teeth of an ultrahard material, such as diamond, as represented by a diamond saw.
For cutting the material by a cutter at a portion protruding from the holding unit, it is preferable to install a support for supporting the material at its protruding free top. The support may favorably be provided with an affixing means, such as a sticky tape, so as to enable the affixing and recovery of the cut off protruding portion as a sample for chemical analysis. The protruding portion support may favorably be arranged on the holding unit directly or on the mount disengageably under intermediation by the setting mount or so on.
For the material preparation using the apparatus described above, the material is first held in the holder of the holding unit, preferably in a state embedded in a filler filled in the holder, and is settled by an assist of a settling member, if present. The settling of the material may be assisted by the protruding portion support disposed on the mount, if the mount is present, by resting the protruding portion of the material on it. Dry ice particles are then placed in the dry ice wells so as to heap the dry ice particles around and over the material.
Dry ice has a sublimation temperature of minus 78.5xc2x0 C. at atmosphere pressure, so that the material will be frozen substantially instantaneously and the ambient atmosphere is replaced by inert carbon dioxide gas. Due to the instantaneous freezing of the material, there occurs no growth of ice crystals within the tissue and, in addition, due to the exclusion of oxygen, no denaturing by the influence of ice, oxygen and heat can be brought about. The material is fixed by solidification of the filler by the low temperature.
In this state, the cutter is slid or rotated in the cutting space to effect cutting of the material, whereby a cut face or a cut rift is formed on the so-cut material while the frictional heat is absorbed by dry ice so that the material is maintained under an inert atmosphere at a temperature of minus 78.5xc2x0 C. Due to the solidified state of the material together with the filler, soft tissues, such as plant root and the like, can be cut and the cut fragments are scattered away without contaminating the cut face of the material. By shaving shallowly the cut face by the cutter blade, a mirror-finished surface can be obtained. Here, the cut and shaven fragments are removed by being captured in the dry ice and a uniform and contaminant-free mirror surface is formed on the material.
The so-prepared material is taken out from the holding unit and used for each specific purpose, while it may favorably be used as a sample for analysis or so on. The method of analysis according to the present invention is effected using the material given above as the sample for analysis or so on. When a sample for analysis or so on is prepared by forming a cut face and/or a cut rift on the material, the so-prepared sample may be taken off together with the sample holder from the mount and set as such on an analyzing apparatus for performing analysis, observation, recording and so on. These examination procedures may be performed either in the frozen state of the sample or in a state after the sample has been warmed to normal temperature in, for example, a desiccator, in order to prevent dew condensation. Samples having the cut face can be examined by analysis, such as a spectroanalysis, by irradiating the cut face with a beam of an electromagnetic wave, by observation under a microscope or with photography and by recording and measurements of the configuration etc. with an image processor or the like. When a cut rift is formed in the sample in the direction parallel to the cut face, an accurate mass spectroscopic analysis can be realized by vaporizing the constituent substances by irradiating the formed slice with a laser beam. Using such a sample, analysis of trace components, which has hitherto been impossible due to light scattering, can be realized, since the sample can be settled in a posture in which the cut face is vertical to the optical axis. The cut face can be formed in a plane at a definite distance from the front end of the sample holder, permitting thus a quantitative analysis of a number of samples under the same condition, whereby the analysis accuracy is increased. When a mirror surface is formed by shaving after the cut face or the cut rift has been prepared, light scattering is prevented and the analysis accuracy can further be increased.
Due to the condition of cutting of the material under a state frozen by dry ice, the sample does not suffer from deformation, destruction and denaturing and can be used for analysis or so on, so that analysis, observation and so on of the exact internal state of the sample are made possible with a high accuracy. An influence of carbon dioxide gas evolved from dry ice on the analysis accuracy can be minimized, since such gas can be removed easily.
There occurs no denaturing in the so-cut material and in the protruding portion thereof, since freezing occurs instantaneously, so that the original state can be restored after thawing. When a seed of a plant serves as the material, the embryo keeps its germing potential and, thus, is permitted to grow. Therefore, it is possible to select superior seeds by the sample analysis and to multiplicate contemplated seeds by cultivating such plants by growing from the embryos of the selected seeds. Here, selection of the seed can be attained without suffering from any influence by the analytical operation, by settling the seed in such a posture that its embryo is in the inside of the holder. The protruding portion cut off may be used as a sample for analyzing the composition thereof by chemical analysis or for other purposes. When the prepared material is used for other purposes than the sample for analyses, namely, for example, when silicon crystal is cut into a silicon wafer, the intrinsic components and physical and chemical properties before the preparation are retained, since no denaturing occurs.
According to the present invention, a material is cut under a condition in which the material is frozen with gas phase replacement by dry ice, so that a cut face and/or cut rift can be formed by a simple construction and simple operation while preventing deformation, destruction and denaturing of the material and, thus, a highly accurate analysis and so on can be realized when the prepared material is used for such analysis and so on.
When the holder is filled with a filler and the material is embedded therein and, then, the filler is frozen by dry ice, an easy fixation of the material can be realized and objects, of which fixation is not easy, such as seeds of plants, can easily be fixed.
By arranging a support for supporting the portion protruding from the holder, displacement of the material due to vibration etc. upon cutting by the cutter can be prevented and the material can be cut precisely. When the support is provided with an affixing means, the protruding portion cut off can be recovered and utilized effectively for analysis or so on.